Machines that are capable of picking a carton from flat folded tubular blank stock and erecting the carton are known in the art. Typically, a plurality of flat folded tubular carton blanks are fed into a magazine from which the carton blanks are sequentially withdrawn by, for example, a vacuum picking/erecting mechanism.
U.S. Pat. Nos. 2,881,021 and 3,242,827, and European Patent Application No. 472,182A1, describe three such vacuum picking/erecting mechanisms. In each of the devices described in these references, the vacuum picking/erecting mechanism operates to grasp the outermost carton blank from the magazine through the application of sub-atmospheric pressure and to pull the carton blank to an erect state. In the U.S. Pat. No. '021 patent, the flat folded carton is grasped by a picking arm and is completely unfolded solely through the use of a lever arm that applies diagonal pressure to the carton blank. In the U.S. Pat. No. '827 patent, a lever arm is not employed. Instead, the picked carton blank is unfolded by a further suction mechanism that exerts a pulling force on an opposing panel of the carton blank. The unfolded carton is then guided into position for further processing to form a filled and sealed container. The European Application discloses a device that uses a roller in combination with a vacuum plate to pick and erect the carton blank.
One of the significant limitations of such prior art machines is their inability to operate simply and reliably at high rates of speed. For example, in the case of the lever operated unfolding mechanism of the device disclosed in the U.S. Pat. No. '021 patent, there is a problem with providing adequate air flow into the carton blank as it is picked and unfolded. Because the tubular blanks are virtually flat and, further, are compressed under the weight of other carton blanks during shipping and storage, it is difficult to separate opposing panels. It therefore becomes necessary to provide for adequate air flow into the interior of each carton blank as it is unfolded. If there is insufficient air flow into the carton blank, the carton will not unfold into an "open" or erect position but, rather, will simply fold over upon itself, re-collapsing to a "closed" position. Thus, when such a lever type unfolding mechanism is employed, the lever arm must operate at a sufficiently low rate of speed to allow adequate time for the carton blank to receive air at its interior.
Machines which employ a further suction mechanism to unfold the carton blank, such as the one disclosed in the U.S. Pat. No. '827 patent, and those that use a roller in combination with a vacuum plate, such as the one disclosed in European Patent Application No. 472,182A1, suffer from the typical problems inherent in more complicated systems. Since these mechanisms involve a greater number of parts, they inherently have greater initial costs, maintenance expenses, and noise levels.